Analysis of the vasomotor waves observed during cardiopulmonary bypass

From the data of the vasomotor waves (VMW) previously reported, we attempted to retrieve information of the gain and the dead-time of the feedback circuit involved. A mathematical analysis revealed a certain relationship between the gain and the dead-time for the VMW to occur in three models. Combining our result with the data of animal experiments obtained by other researchers, we could exclude one of three models, thereby setting the area of existence of gain-delay value. When we apply a value of 3.4 sec for dead-time, as extrapolated from the animal data, the static gain of the system is between 2.2 and 4.0. Contrary to those observed in animal experiments and to our own original speculation, the VMW in man during cardiopulmonary bypass is likely caused via baroreceptor (carotid sinus) reflex rather than through cerebral ischemic response.